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High Pressure Piston Valve Design-1000psi

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 15, 2012 11:19 am

vakimo wrote:By the way would a nylon piston work for this? its a pain in ass to lathe, but it would be lighter and more shock absorbant


Delrin is a joy to machine ;)

I would make it delrin or nylon only. No need for sealing rubber at the pressures you are going to provided all the surfaces are true. Also, I wouldn't bother with o-rings or equalisation holes. Just make it a tight fit and you're good to go.
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Unread postAuthor: al-xg » Thu Mar 15, 2012 11:43 am

Right as more substantial design variations are being proposed, I put my lunch break to use :)
Image
Ok, I got a bit carried away and made it a radial seal piston. A normal sealing face could also be used with a very short seat tube, at the expense of a bit of flow but then the piston wouldn't need holding back (the 4 bolts on the drawing, doesn't have to be bolts though).

If you're machining most of the parts from stock, you may as well make fewer more specialised parts.

The flow of through a QEV like that would be higher.
You could even angle the QEV at say 30degrees from the barrel to reduce losses through the T.
Of course that would mean having an equaly slanted magazine if you were going for semi-auto later on.
Inline would be better, but the loading system would have to be different.

A more practical thing to notice is the use of O-rings for sealing the various parts.
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 15, 2012 2:22 pm

*fap fap fap*

Beautiful, I really need to get realview to work!
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Unread postAuthor: vakimo » Thu Mar 15, 2012 6:05 pm

I would make it delrin or nylon only. No need for sealing rubber at the pressures you are going to provided all the surfaces are true. Also, I wouldn't bother with o-rings or equalisation holes. Just make it a tight fit and you're good to go.


good to hear, that would simply the design. and make less headaches :)
If you have a lathe then wouldn't it be easier to just make those top and bottom holding plate things?.

In order to use the lathes i have to have to be supervised unfortunately, so im trying to limit lathe use.

I have a feeling that your rubber sealing face is going to get ripped straight off during piloting.

Yes, that happened a lot on the last high pressure cannon i worked on. Those bolts you circled were to keep the the two pipe rings on either end. they shouldn't actually have any force on them.

al-xg, i really like that design, and i think ill be able to use parts of it. id like to have a large reserve of air and be able to expand it if need be though, so i think the seperate air chamber would be necessary.

Also, is it difficult to achieve such high pressure seals with o- rings? i assumed it would, so that's why i used more of a clamping style.
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Unread postAuthor: al-xg » Thu Mar 15, 2012 6:47 pm

O-ring seals can be used way past 1000psi if the grooves are the right size and the right hardness o-ring is used for the application.
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Unread postAuthor: vakimo » Thu Mar 15, 2012 7:46 pm

Okay, would you happen to know of a good link that i could learn how to do that? that would really simplify the design.

Also, thanks for the CAD image. it's really sparked some ideas :D
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Unread postAuthor: Gippeto » Fri Mar 16, 2012 12:43 am

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